package net.sourceforge.jsocks;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

/**
 * Datagram socket to interract through the firewall.<BR>
 * Can be used same way as the normal DatagramSocket. One should be carefull
 * though with the datagram sizes used, as additional data is present in both
 * incomming and outgoing datagrams.
 * <p>
 * SOCKS5 protocol allows to send host address as either:
 * <ul>
 * <li>IPV4, normal 4 byte address. (10 bytes header size)
 * <li>IPV6, version 6 ip address (not supported by Java as for now). 22 bytes
 * header size.
 * <li>Host name,(7+length of the host name bytes header size).
 * </ul>
 * As with other Socks equivalents, direct addresses are handled transparently,
 * that is data will be send directly when required by the proxy settings.
 * <p>
 * <b>NOTE:</b><br>
 * Unlike other SOCKS Sockets, it <b>does not</b> support proxy chaining, and
 * will throw an exception if proxy has a chain proxy attached. The reason for
 * that is not my laziness, but rather the restrictions of the SOCKSv5 protocol.
 * Basicaly SOCKSv5 proxy server, needs to know from which host:port datagrams
 * will be send for association, and returns address to which datagrams should
 * be send by the client, but it does not inform client from which host:port it
 * is going to send datagrams, in fact there is even no guarantee they will be
 * send at all and from the same address each time.
 */
public class Socks5DatagramSocket extends DatagramSocket {

	InetAddress relayIP;
	int relayPort;
	Socks5Proxy proxy;
	private boolean server_mode = false;
	UDPEncapsulation encapsulation;

	/**
	 * Construct Datagram socket for communication over SOCKS5 proxy server.
	 * This constructor uses default proxy, the one set with
	 * Proxy.setDefaultProxy() method. If default proxy is not set or it is set
	 * to version4 proxy, which does not support datagram forwarding, throws
	 * SocksException.
	 */
	public Socks5DatagramSocket() throws SocksException, IOException {
		this(Proxy.defaultProxy, 0, null);
	}

	/**
	 * Used by UDPRelayServer.
	 */
	Socks5DatagramSocket(boolean server_mode, UDPEncapsulation encapsulation,
			InetAddress relayIP, int relayPort) throws IOException {
		super();
		this.server_mode = server_mode;
		this.relayIP = relayIP;
		this.relayPort = relayPort;
		this.encapsulation = encapsulation;
		this.proxy = null;
	}

	/**
	 * Construct Datagram socket for communication over SOCKS5 proxy server. And
	 * binds it to the specified local port. This constructor uses default
	 * proxy, the one set with Proxy.setDefaultProxy() method. If default proxy
	 * is not set or it is set to version4 proxy, which does not support
	 * datagram forwarding, throws SocksException.
	 */
	public Socks5DatagramSocket(int port) throws SocksException, IOException {
		this(Proxy.defaultProxy, port, null);
	}

	/**
	 * Construct Datagram socket for communication over SOCKS5 proxy server. And
	 * binds it to the specified local port and address. This constructor uses
	 * default proxy, the one set with Proxy.setDefaultProxy() method. If
	 * default proxy is not set or it is set to version4 proxy, which does not
	 * support datagram forwarding, throws SocksException.
	 */
	public Socks5DatagramSocket(int port, InetAddress ip)
			throws SocksException, IOException {
		this(Proxy.defaultProxy, port, ip);
	}

	/**
	 * Constructs datagram socket for communication over specified proxy. And
	 * binds it to the given local address and port. Address of null and port of
	 * 0, signify any availabale port/address. Might throw SocksException, if:
	 * <ol>
	 * <li>Given version of proxy does not support UDP_ASSOCIATE.
	 * <li>Proxy can't be reached.
	 * <li>Authorization fails.
	 * <li>Proxy does not want to perform udp forwarding, for any reason.
	 * </ol>
	 * Might throw IOException if binding dtagram socket to given address/port
	 * fails. See java.net.DatagramSocket for more details.
	 */
	public Socks5DatagramSocket(Proxy p, int port, InetAddress ip)
			throws SocksException, IOException {
		super(port, ip);
		if (p == null)
			throw new SocksException(Proxy.SOCKS_NO_PROXY);
		if (!(p instanceof Socks5Proxy))
			throw new SocksException(-1,
					"Datagram Socket needs Proxy version 5");

		if (p.chainProxy != null)
			throw new SocksException(Proxy.SOCKS_JUST_ERROR,
					"Datagram Sockets do not support proxy chaining.");

		proxy = (Socks5Proxy) p.copy();

		ProxyMessage msg = proxy.udpAssociate(super.getLocalAddress(),
				super.getLocalPort());
		relayIP = msg.ip;
		if (relayIP.getHostAddress().equals("0.0.0.0"))
			relayIP = proxy.proxyIP;
		relayPort = msg.port;

		encapsulation = proxy.udp_encapsulation;

		// debug("Datagram Socket:"+getLocalAddress()+":"+getLocalPort()+"\n");
		// debug("Socks5Datagram: "+relayIP+":"+relayPort+"\n");
	}

	/**
	 * Closes datagram socket, and proxy connection.
	 */
	@Override
	public void close() {
		if (!server_mode)
			proxy.endSession();
		super.close();
	}

	private byte[] formHeader(InetAddress ip, int port) {
		Socks5Message request = new Socks5Message(0, ip, port);
		request.data[0] = 0;
		return request.data;
	}

	/**
	 * Address assigned by the proxy, to which datagrams are send for relay. It
	 * is not necesseraly the same address, to which other party should send
	 * datagrams.
	 * 
	 * @return Address to which datagrams are send for association.
	 */
	@Override
	public InetAddress getLocalAddress() {
		if (server_mode)
			return super.getLocalAddress();
		return relayIP;
	}

	/**
	 * Returns port assigned by the proxy, to which datagrams are relayed. It is
	 * not the same port to which other party should send datagrams.
	 * 
	 * @return Port assigned by socks server to which datagrams are send for
	 *         association.
	 */
	@Override
	public int getLocalPort() {
		if (server_mode)
			return super.getLocalPort();
		return relayPort;
	}

	/**
	 * This method checks wether proxy still runs udp forwarding service for
	 * this socket.
	 * <p>
	 * This methods checks wether the primary connection to proxy server is
	 * active. If it is, chances are that proxy continues to forward datagrams
	 * being send from this socket. If it was closed, most likely datagrams are
	 * no longer being forwarded by the server.
	 * <p>
	 * Proxy might decide to stop forwarding datagrams, in which case it should
	 * close primary connection. This method allows to check, wether this have
	 * been done.
	 * <p>
	 * You can specify timeout for which we should be checking EOF condition on
	 * the primary connection. Timeout is in milliseconds. Specifying 0 as
	 * timeout implies infinity, in which case method will block, until
	 * connection to proxy is closed or an error happens, and then return false.
	 * <p>
	 * One possible scenario is to call isProxyactive(0) in separate thread, and
	 * once it returned notify other threads about this event.
	 * 
	 * @param timeout
	 *            For how long this method should block, before returning.
	 * @return true if connection to proxy is active, false if eof or error
	 *         condition have been encountered on the connection.
	 */
	public boolean isProxyAlive(int timeout) {
		if (server_mode)
			return false;
		if (proxy != null) {
			try {
				proxy.proxySocket.setSoTimeout(timeout);

				int eof = proxy.in.read();
				if (eof < 0)
					return false; // EOF encountered.
				else
					return true; // This really should not happen

			} catch (InterruptedIOException iioe) {
				return true; // read timed out.
			} catch (IOException ioe) {
				return false;
			}
		}
		return false;
	}

	/**
	 * Receives udp packet. If packet have arrived from the proxy relay server,
	 * it is processed and address and port of the packet are set to the address
	 * and port of sending host.<BR>
	 * If the packet arrived from anywhere else it is not changed.<br>
	 * <B> NOTE: </B> DatagramPacket size should be at least 10 bytes bigger
	 * than the largest packet you expect (this is for IPV4 addresses). For
	 * hostnames and IPV6 it is even more.
	 * 
	 * @param dp
	 *            Datagram in which all relevent information will be copied.
	 */
	@Override
	public void receive(DatagramPacket dp) throws IOException {
		super.receive(dp);

		if (server_mode) {
			// Drop all datagrams not from relayIP/relayPort
			int init_length = dp.getLength();
			int initTimeout = getSoTimeout();
			long startTime = System.currentTimeMillis();

			while (!relayIP.equals(dp.getAddress())
					|| relayPort != dp.getPort()) {

				// Restore datagram size
				dp.setLength(init_length);

				// If there is a non-infinit timeout on this socket
				// Make sure that it happens no matter how often unexpected
				// packets arrive.
				if (initTimeout != 0) {
					int newTimeout = initTimeout
							- (int) (System.currentTimeMillis() - startTime);
					if (newTimeout <= 0)
						throw new InterruptedIOException(
								"In Socks5DatagramSocket->receive()");
					setSoTimeout(newTimeout);
				}

				super.receive(dp);
			}

			// Restore timeout settings
			if (initTimeout != 0)
				setSoTimeout(initTimeout);

		} else if (!relayIP.equals(dp.getAddress())
				|| relayPort != dp.getPort())
			return; // Recieved direct packet
		// If the datagram is not from the relay server, return it it as is.

		byte[] data;
		data = dp.getData();

		if (encapsulation != null)
			data = encapsulation.udpEncapsulate(data, false);

		int offset = 0; // Java 1.1
		// int offset = dp.getOffset(); //Java 1.2

		ByteArrayInputStream bIn = new ByteArrayInputStream(data, offset,
				dp.getLength());

		ProxyMessage msg = new Socks5Message(bIn);
		dp.setPort(msg.port);
		dp.setAddress(msg.getInetAddress());

		// what wasn't read by the Message is the data
		int data_length = bIn.available();
		// Shift data to the left
		System.arraycopy(data, offset + dp.getLength() - data_length, data,
				offset, data_length);

		dp.setLength(data_length);
	}

	/**
	 * Sends the Datagram either through the proxy or directly depending on
	 * current proxy settings and destination address. <BR>
	 * 
	 * <B> NOTE: </B> DatagramPacket size should be at least 10 bytes less than
	 * the systems limit.
	 * 
	 * <P>
	 * See documentation on java.net.DatagramSocket for full details on how to
	 * use this method.
	 * 
	 * @param dp
	 *            Datagram to send.
	 * @throws IOException
	 *             If error happens with I/O.
	 */
	@Override
	public void send(DatagramPacket dp) throws IOException {
		// If the host should be accessed directly, send it as is.
		if (!server_mode) {
			super.send(dp);
			// debug("Sending directly:");
			return;
		}

		byte[] head = formHeader(dp.getAddress(), dp.getPort());
		byte[] buf = new byte[head.length + dp.getLength()];
		byte[] data = dp.getData();
		// Merge head and data
		System.arraycopy(head, 0, buf, 0, head.length);
		// System.arraycopy(data,dp.getOffset(),buf,head.length,dp.getLength());
		System.arraycopy(data, 0, buf, head.length, dp.getLength());

		if (encapsulation != null)
			buf = encapsulation.udpEncapsulate(buf, true);

		super.send(new DatagramPacket(buf, buf.length, relayIP, relayPort));
	}

	// PRIVATE METHODS
	// ////////////////

	/**
	 * This method allows to send datagram packets with address type DOMAINNAME.
	 * SOCKS5 allows to specify host as names rather than ip addresses.Using
	 * this method one can send udp datagrams through the proxy, without having
	 * to know the ip address of the destination host.
	 * <p>
	 * If proxy specified for that socket has an option resolveAddrLocally set
	 * to true host will be resolved, and the datagram will be send with address
	 * type IPV4, if resolve fails, UnknownHostException is thrown.
	 * 
	 * @param dp
	 *            Datagram to send, it should contain valid port and data
	 * @param host
	 *            Host name to which datagram should be send.
	 * @throws IOException
	 *             If error happens with I/O, or the host can't be resolved when
	 *             proxy settings say that hosts should be resolved locally.
	 * @see Socks5Proxy#resolveAddrLocally(boolean)
	 */
	public void send(DatagramPacket dp, String host) throws IOException {
		dp.setAddress(InetAddress.getByName(host));
		super.send(dp);
	}

	/*
	 * ======================================================================
	 * 
	 * //Mainly Test functions //////////////////////
	 * 
	 * private String bytes2String(byte[] b){ String s=""; char[] hex_digit = {
	 * '0','1','2','3','4','5','6','7','8','9', 'A','B','C','D','E','F'};
	 * for(int i=0;i<b.length;++i){ int i1 = (b[i] & 0xF0) >> 4; int i2 = b[i] &
	 * 0xF; s+=hex_digit[i1]; s+=hex_digit[i2]; s+=" "; } return s; } private
	 * static final void debug(String s){ if(DEBUG) System.out.print(s); }
	 * 
	 * private static final boolean DEBUG = true;
	 * 
	 * 
	 * public static void usage(){ System.err.print(
	 * "Usage: java Socks.SocksDatagramSocket host port [socksHost socksPort]\n"
	 * ); }
	 * 
	 * static final int defaultProxyPort = 1080; //Default Port static final
	 * String defaultProxyHost = "www-proxy"; //Default proxy
	 * 
	 * public static void main(String args[]){ int port; String host; int
	 * proxyPort; String proxyHost; InetAddress ip;
	 * 
	 * if(args.length > 1 && args.length < 5){ try{
	 * 
	 * host = args[0]; port = Integer.parseInt(args[1]);
	 * 
	 * proxyPort =(args.length > 3)? Integer.parseInt(args[3]) :
	 * defaultProxyPort;
	 * 
	 * host = args[0]; ip = InetAddress.getByName(host);
	 * 
	 * proxyHost =(args.length > 2)? args[2] : defaultProxyHost;
	 * 
	 * Proxy.setDefaultProxy(proxyHost,proxyPort); Proxy p =
	 * Proxy.getDefaultProxy(); p.addDirect("lux");
	 * 
	 * 
	 * DatagramSocket ds = new Socks5DatagramSocket();
	 * 
	 * 
	 * BufferedReader in = new BufferedReader( new
	 * InputStreamReader(System.in)); String s;
	 * 
	 * System.out.print("Enter line:"); s = in.readLine();
	 * 
	 * while(s != null){ byte[] data = (s+"\r\n").getBytes(); DatagramPacket dp
	 * = new DatagramPacket(data,0,data.length, ip,port);
	 * System.out.println("Sending to: "+ip+":"+port); ds.send(dp); dp = new
	 * DatagramPacket(new byte[1024],1024);
	 * 
	 * System.out.println("Trying to recieve on port:"+ ds.getLocalPort());
	 * ds.receive(dp); System.out.print("Recieved:\n"+
	 * "From:"+dp.getAddress()+":"+dp.getPort()+ "\n\n"+ new
	 * String(dp.getData(),dp.getOffset(),dp.getLength())+"\n" );
	 * System.out.print("Enter line:"); s = in.readLine();
	 * 
	 * } ds.close(); System.exit(1);
	 * 
	 * }catch(SocksException s_ex){ System.err.println("SocksException:"+s_ex);
	 * s_ex.printStackTrace(); System.exit(1); }catch(IOException io_ex){
	 * io_ex.printStackTrace(); System.exit(1); }catch(NumberFormatException
	 * num_ex){ usage(); num_ex.printStackTrace(); System.exit(1); }
	 * 
	 * }else{ usage(); } }
	 */

}
